Dry Fly Fishing for Trout: Expert Secrets from Beginner to Advanced

Mastering dry fly fishing for trout on a river is often seen as the peak of fly fishing. Here, Dr Paul Gaskell shows you how...

Busting some myths on dry fly fishing for trout

In fact, once you have nailed down your fly casting skills, dry fly can be one of the more straight-forward methods of fly fishing. How can I possibly say that with a straight face?

Well:

In other words, so many of the things that you need to develop a sixth sense for in sub-surface fishing in three dimensions are laid out right in front of you for a lot of dry fly fishing situations. As an aside, you can compare dry fly at wet by clicking my guide to wet fly fishing. 

The Aim of the Game

The basic idea is to cast your fly upstream of the fish – just far enough that it can see and then easily intercept the fly as it drifts down over their head. As you see the fish take the fly into its mouth AND then turn back down to its holding depth, you set the hook by lifting the rod tip.

For getting started in dry fly fishing, keeping that simple idea in mind is more than good enough to get you into fish (whether you land them or not depends on what happens after that). 

Sounds pretty simple right? Well, of course, there CAN be a bit more to it than that, but we'll break the "what happens if Plan A doesn't work" down into bite-size chunks from here on in...

As well as one nymph capture - Mayfly Project Ambassador Susan Skrupa (below) shows a typical day of dry fly fishing for trout while trying out her Orvis Clearwater 3-weight on the Cressbrook and Litton fisheries of the Derbyshire River Wye (note, Fishing Discoveries has no financial affiliate commissions with Orvis - it's "just the facts Ma'am").

This is possibly the last of only two or three rivers in England to support self-sustaining/stream-bred populations of rainbow trout as well as brown trout. It's also a natural opportunity to express Fishing Discoveries' support of the 50/50 on the water initiative:

Basic River Trout Dry Fly Gear Rundown

Tips for a healthy(!) and effective dry fly collection

It is very easy to get carried away and have far too many dry flies. Few people are immune to this – and they are really satisfying to tie. In fact, feel free to indulge in a bit of excess if you enjoy it...

 Just try not to lose the fun by getting a bit too fanatical in either direction (whether that’s “minimalist” or “hoarder”). Of course, if you’re enjoying going down a particular rabbit hole, go for it.

Dry fly fishing for trout: Insect Biology & Fly Design

Having a basic idea of what river flies hatch on your stream can be helpful. In fact, knowing more about the habits of the flies that trout feed on can really up your game. However, don't be put off if your entomology skills are a bit lacking - there is huge value in basic observation while you are out on stream. In fact, this skill is critical to success in dry fly fishing for trout:

Example River-fly Lifecycles

To help you make sense of the stuff you'll see on stream, here's a whistlestop tour of important points. So, first things first...

All river flies (flying insects that have aquatic larval stages) start life as an egg, then their aquatic larvae (called nymphs) grow and moult their skins several times.

Some (e.g. midges and caddis) have a "pupa" stage where the body-parts are re-organised to become closer to the adult body-plan. In fact, when caddis flies pupate and then move from the riverbed to hatch - they are known as "pharate adults" (although those adults on the way to the surface are often mistakenly called "caddis pupae").

In fact the pharate adults are fully-formed adult flies which are covered in a kind of membrane which provides them with a temporary oxygen supply to get them to the surface - where a different system (of "spiracles" and "tracheae") will let them breathe air! The important things for you to know are that Caddis flies can look a little bit like moths and there are hundreds of different species. PLUS:

No matter what family or species, the adult, flying insect hatches from either the nymph or pupa...

Some insects hatch at the surface of the water. Those surface-hatching insects (like mayflies and midges) still need to get through the surface film - a task that would be the equivalent of you breaking through your kitchen table! Thanks to Stuart Crofts, I now know how they achieve this incredible feat...

Their trick (which you can see in action above) is to have the nymphs/pupae "glue" themselves to the underside of the surface-film of the water using special "water-loving" cells on their thorax. That gives them something to pull on (otherwise if they just pushed up against the surface, they'd simply bounce off).

The second part of the trick is to use waxy water-repelling cells towards the centre of the "anchoring" ring of water-loving cells. Those waxy cells push apart the water molecules to make an "escape hatch" for the adult fly to push through as they escape their larval/pupal skin.

During that struggle to break through the surface, the insect is known as an emerger. This is an incredibly important lifecycle stage when you are dry fly fishing for trout. It is at this point that the flies are least likely to escape - and trout latch onto them as they are glued half in/half out of that surface film.

Other species (e.g. large stoneflies), crawl up onto rocks, logs or plant-stems as nymphs - and then split their skins to allow the adult fly to crawl out. However, the resulting adults may crash-land on the water during the mating scramble - or the females will return to the water to lay eggs. So they can still create viable targets for the dry fly angler to imitate.

The mayflies (or upwing flies) are unique in the insect world - because they have TWO adult stages. The first stage is called a "dun" by anglers - that is what hatches out from the water surface. Then those drab duns fly to the nearest vegetation so that they can moult again to become the much more sparkly and showy "spinner". That is the sexually-mature form which forms the dancing mating swarms before the females return to the water to lay eggs. 

Some lay eggs on the surface of the water before dying (and becoming a "spent spinner"). Others (including Baetis species of upwing flies) crawl down vegetation, rocks or bridge-footings so that they can lay eggs on the underside of rocks on the riverbed. The "spent spinners" of those species are - therefore - washed along the riverbed (and not the surface).

ALWAYS REMEMBER THAT YOU CAN "DOCTOR" YOUR FLY (BY TRIMMING, PLUCKING OR CHOOSING EXACTLY WHICH PART OF THE FLY TO APPLY FLOATANT TO) AND/OR CHANGE HOW YOU MANIPULATE IT TO CREATE THE RIGHT IMPRESSION.

AS LONG AS THE SIZE IS ACCEPTABLE - THE "WRONG" FLY DOCTORED AND PRESENTED IN THE RIGHT WAY WILL BE VERY SUCCESSFUL.

Example Fly Designs

I've provided some suggestions to help you match up some of the types of bugs you'll find on stream to artificial patterns below. Always bear in mind that there's more than one way to skin a cat - in other words, several patterns can imitate the same natural fly! There's no such thing as a hatch of "Parachute Adams" or "F-Flies" - but there are small olive mayfly and needle-fly hatches...

Before I share those suggested flies, it is worth understanding the difference between the different FUNCTIONAL DESIGNS of Dry Flies. This includes the difference between a "Parachute Hackle" and a conventional hackle. Because more of the fibres in a parachute hackle will lay across the water (instead of poking down into it), it is often easier to keep that style of fly afloat for long periods.

Both of the above patterns probably best represent "duns" or adult insects (or at least are a tolerably-good imitation of that situation). For more pronounced "emerger" imitations, a dropped/angled abdomen is a powerful trigger. The shape of the hook and position of the part of the fly which makes the fly float can control this. The buoyant, fuzzy "CDC" (cul-de-canard) feathers from close to the preen gland on ducks is very good for this purpose (as well as curved-abdomen parachute hackle flies in the "klinkhåmer special" mould). See below for examples in the "Abdomen Angle" section...

Abdomen Angle: Functional Emerger Flies

I often hear anglers talk about "emergers" with tungsten beads or other well-sunk wet fly or nymph patterns. What they are talking about is a fly with obvious legs or hackles. That impression isn't quite right though (completely-mature adult flies that have been drowned and well-sunk have legs and wings sticking out all over the place. That has nothing specifically to do with the process of emerging from the nymph). 

The key detail that the word "emerger" is telling you is that the adult fly is struggling half in/half out of its nymphal "shuck". Because the word "emerger" is used by dry fly/surface-pattern anglers, we are ONLY talking about those species that emerge AT THE SURFACE OF THE WATER. This has special significance when dry fly fishing for trout - because trout LOVE a sure thing. Of course, because we fly anglers love a good argument - there are plenty of dry fly anglers who class emergers as nymphs (and vice versa). 

That seems to get too close to a Dr Seuss butter-side up/butter side down parody of nuclear arms races - and that is me veering dangerously off-course...

While an emerger is poking through the surface film it can't swim away and it can't yet fly away. That is a window of vulnerability for a visual predator like a trout.

Let's look at the amazing image captured by Stuart Crofts below to LOCK IN that image of vulnerable prey:

Depending on the temperature/humidity it can take flies a bit longer to struggle free of their nymphal "shuck" (skin). On other days (or for certain species) they might be able to emerge incredibly quickly - but weather conditions might slow down how quickly they can get their wings working. Those are the kind of things that influence whether trout are eating duns or emergers.

Further on in this article I'll give you some clues to look for in the way that trout rise which can indicate whether they are eating duns or emergers.

Before we get to that, check out another two FUNCTIONAL choices for fly design (this time specifically for emergers):

There are many ways to achieve a hanging abdomen for an emerger pattern (see photos of different parachute dressings below for examples). The two diagrams above show options using cul-de-canard feather (which is buoyant more because of its structure of thousands of tiny, fine air-trapping barbs - rather than being coated with preen-gland oil as popular myth would have it).

MANY dry fly floatant chemicals will wick those fine barbs together and make them into a matted, sinking mess. 

However, compounds such as Loon Aquel will actually help cdc float for longer. We have no affiliation with Loon, it's just what we use - and you can experiment to find others that also work. The other product that is useful with cdc is hydrophobic fumed silica (one commercial brand of this is Frog's Fanny - again no affiliation). This fine powder actively drives out moisture when dabbed onto cdc with a brush applicator - and it is a game-changer for reviving cdc flies such as the famous Slovenian F-Fly created by Marjan Fratnik.

The main take-home message from the "emerger" diagrams above is that you can tweak the abdomen angle of your artificial fly to imitate characteristics of different natural insects.

Suggested Dressing Styles Matched to "Bread and Butter" Natural Insect Species:

Please DON'T be restricted by these patterns - they are all just examples of design principles. In the same way, don't dismiss them because another fly that imitates the same thing has a more famous name...

Also - size them to suit your local insects; that's why I haven't put hook sizes on these! Purely for comparison, the Griffiths Gnat is a size 20.

Local Specialities

Where you have famous and characteristic hatches at certain times of the year, there will probably be local fly shops with great patterns available. For example there might be a specific hatch of lovely big stoneflies like the salmon fly in your river. 

Similarly, larger mayfly imitations (such as greendrakes) are useful for those specific hatch periods in the river where they occur.

Dry Fly Fishing For Trout: Almost Unknown Core Principles

Before we even get into what most anglers consider the fundamentals of dry fly fishing for trout (such as “upstream” versus “downstream” schools of thought), I want to introduce what I think are true basic principles.

Prey image

The size of the fly is probably the single most important thing – most fly designs feature a body that is longer than it is wide with “stuff that sticks out” to look something like legs, wings and maybe tails. Where and how a dry fly sits in the film is another key element – but even the “wrong” fly can often be made to float in something like the right way (either by trimming bits or being selective in exactly which bits of your fly you apply floatant to - as mentioned).

Simple Rules

Side-note, behavioural ecologists refer to the “search image” used by visual predators to recognise prey. Basically, predators use a greatly simplified set of "rules" to identify "food".  Even something as basic as the ratios of length to width and the plane of movement of a "stick-drawing" or match-stick have been shown in experiments to be more than enough to trigger feeding…

It’s worth bearing the above scientific data in mind when you are being told that you need the correct number of turns of rib on your dry flies “otherwise the fish will refuse it”.

Applying to your own waters

For your stream it is as well to know the basic size of river flies that hatch from (or terrestrial bugs that fall onto) the water’s surface at each stage of the season. Don’t rely on the calendar too much though. Again, it is much better to observe what is hatching (and what is being taken by the fish more importantly).

The selection of “suggestive” flies in the photos above are tried and tested. They are also often less “rigid” and “robotic” when fished (compared to super-realistic dressings). You will have plenty of time to experiment with and settle on your own favourite selections to cover your own waters.

Casting Tips when Dry Fly Fishing for Trout

Main choices for landing your fly

#1 Fly first (angled-down cast)

For this (more conventional) style, your casting loops will be parallel to the water and the fly will drift down more slowly onto the surface. It is best to separate the splash of your line landing from that of your fly by using as long a leader as you can cope with in the conditions.  

As with any kind of fly fishing, try to hold as much line off the water as possible. As well as making your hook-sets more effective, it also helps keep your fly line out of nagging currents. The more that conflicting currents pull your line around, the sooner any slack in your leader will disappear and make your fly drag around weirdly. That tends to result in unnatural and unattractive (to fish) movement of your fly.

Tuning your Rigs for Soft Landings after Casting

When starting out, try using around 9’ of tapered leader and at least 2’ of level tippet in the 5x or 6x (~4.5-lb or 3-lb). Working up to total “leader + tippet” length in the 15’ to 18' range is particularly helpful for this style of dry fly fishing. If you’re fishing tiny midges in size 18 or 20 and below, it is certainly worth thinking about 7x tippet for those.

Amount of “lead” - vital to successful dry fly fishing for trout

You need to assess the Holding Depth of the fish: 

These diagrams will help you lock in a good benchmark for lead-distances when dry fly fishing for trout:

If nothing else, understand that you have to cast further upstream of a deep-lying fish. Trout can hang at almost any height in the water column. If the water is clear enough, they will rise from down near the riverbed during the warmer months. Sometimes they might be hovering just below the surface.

Casting Angles, Line Management & Timing

Depending on where in the world you’re fishing, there’ll be different rules on how you can cast. For some ultra-traditional clubs on – typically English Chalkstreams – you are only allowed to cast your fly at an upstream angle (i.e. the angler must be downstream of the fish).

To a non-angler (or to an angler transitioning to fly fishing from a different discipline), this must seem perversely restrictive. As a fly fishing “lifer”, I would tend to agree! I believe it reduces the scope for skilled anglers. That being said, a great deal of fly fishing’s enjoyment can be taken from immersion in its traditions and rich history. Having an upstream only rule does make it a bit simpler to stick to an etiquette of working upstream - and avoid anglers getting into conflict.

Fishing Upstream

Ironically, without difficult obstacles, the easiest option is an upstream cast (which is one reason it can stifle angling skills development). A basic rule of thumb would be casting approximately 30 to 45 degrees to the current (so that the fly and leader lands in a "lane" beyond the fly line).

If your cast is accurate enough, you’ll land the fly with the right amount of “lead” above the fish AND have enough separation between that fish and the splashdown of the fly line - like this; note the offset angle (short arrow) from directly upstream (the long arrow):

Then it’s a case of recovering the slack in the line by either raising or tracking around with your rod tip at the pace of the current. If necessary, you can also retrieve line with your “non-rod hand” by stripping it through your “trigger finger” on your rod hand.

If the fish doesn’t eat your fly, allow it to drift a safe distance downstream and take in enough line that it won’t make a huge disturbance when you pick off into your next cast. Always start to lift your line slowly and smoothly – so it peels gently off the water as it escapes the surface-tension. SLOOSHING your line off the water will scare any self-respecting trout into the next county.

Downstream Dry Fly

Fishing downstream to spooky fish in shallow, flat water is a very tricky proposition. Get it right, though, and you can be rewarded with fish that other anglers are unable to catch. In a wild fishery, that can mean the biggest and wildest fish that have evaded capture for the longest time.

One reason for the potential effectiveness of fishing dry flies downstream are that the fish, by definition, gets to see the fly before any tippet, leader, fly line or rod.

The proviso for using this approach is that you will need to very carefully (and often slowly) move into position above the fish. If you scare it before you cast, the game is up. Try to think of how you’d need to move if the fish was a rabbit grazing on a patch of open ground rather than a fish in water.

Parachute cast

An essential skill for fishing a dry fly downstream is the parachute cast (below). On the final delivery of your forward cast, instead of following the line down towards the water with your rod tip, gently draw/hold the rod tip up and backwards. With the rod tip finishing in a roughly vertical position, you can then track the natural drift of your fly downstream by lowering your rod at the pace of the current:

It takes a bit of practice to get the judgement of how much additional line/distance you need to allow in your first cast (so that your fly actually has enough line to reach the feeding fish!).

If the target fish doesn’t eat your fly on the first cast, try to lean your rod tip over to gently draw your fly, leader and line away to one side of the fish. You might get lucky and be able to pull everything far enough from the fish to be able to stealthily retrieve your line and gently lift off and make another cast; MAYBE.

Mending your line

When dry fly fishing for trout – or any other species – you will often need to cast your line across corridors of water travelling at different speeds. The idea with “mending” your line is to put some extra line into the faster parts of the current. Making this work relies on positioning that extra line further upstream than the line laying in the slower water. 

That way, you buy some time while the currents eat up the extra slack – before the line comes tight to your fly again and starts to drag it.

The best way to mend for dry fly is to position that line while it is still in the air. This makes the line lay in just the right shape on the water as your fly lands. By doing this, you’re fishing effectively right from the moment your fly touches down.

Timing your casts

It doesn’t matter what angle you are casting to the current, you always need to time your casts carefully. As an absolute baseline, you need to be sure that the fish is feeding confidently you’re your fly passes over it.

Always bear in mind that your first shot at a fish is always your best – so make it count by doing everything you can to avoid spooking it. Try to have the patience to let it establish a regular, confident feeding rhythm after you have got into position to cast. This is WAY more difficult when your target fish is rising sporadically. 

That being said, there are many rivers (usually with reasonably clear water) where a good size caddis imitation or a nice terrestrial beetle "splatted" down on the surface can pull fish up - even if they are not actively rising to a hatch of natural flies. Great training for this style is to get good at reading current features by developing your Euro nymphing tactics.

Timing AND Placing your Casts

Another nearly impossible situation can happen in completely still water (e.g. behind a dam or other structure that holds water back – whether natural or engineered by humans). In still - or very slow - water, fish are more likely to rove around and rise in different spots depending where the food is.

When that happens, the very WORST place to cast is  where the fish just surfaced – since that is the ONE place it is guaranteed NOT to be. In other words, the fish can be rising sporadically in time and also varying their location constantly. At least when a fish is holding one station in flowing water, it might only be the timing that is sporadic!

Your best chance for roving fish is to observe and see if the fish has an established patrol route – and try to intercept it along that path. If all else fails, casting out in a likely spot and leaving your fly can sometimes work.

Expert anglers in New Zealand often talk about this as one of the differences between dry fly fishing for brown trout and targeting rainbows. Big brownies seem a bit more prone to establishing a patrol route in backwater features...whereas the rainbows are a bit more likely to hold station in the faster flows.

Cadence of rising fish

An often overlooked aspect of timing your cast is also to lock into that rhythm of a rising fish. For different sizes of prey item, it will take a different amount of time for the fish to gulp down and be ready to eat the next item. Similarly, the deeper a fish is lying, the longer it takes it to move up to the surface and then back onto station.

Behavioural ecologists call this "handling time" (here's a handy graph showing the handling time for different sizes of mussels for crabs):

For tiny aphids, there is virtually no lag needed because both of the following effects combine:

• Depth - the fish are often stationed just an inch or so below the surface; so it only needs to tilt a fin and angle its head up slightly to gulp down its meal
• Meal size – aphids are so small that they can just be swallowed in one gulp (the trout doesn’t need to subdue its prey or make a couple of gulps to ensure it goes down the gullet).

Successful dry fly anglers learn to match the timing of delivering their fly to to timing of the feeding rhythm of the trout. Too many anglers think their fly has been refused simply because it floated over the fish when it was still returning to its station and/or still gulping down its previous victim.

Rise-Forms: What are they Eating?

Now we are building some pretty sophisticated understanding into the whole deal. The way that fish break the water when they take natural flies from the surface can help you make a better choice of dry fly design. Here is a very quick guide that, although simple, you might find helpful in making fly choices. Note, these are simply decent “best guesses” - not set in stone:

How to Time your hookset when dry fly fishing for trout

As well as timing of delivering your cast, you need to tune the timing of your hookset to the fish you are targeting. Ideally the fish needs to have turned down with your fly before you set the hook. By the same token, you don’t want to leave it so long that the trout has decided your artificial fly feels more like hard debris than juicy insect (and spat it out).

Avoiding drag with “competition” style dry fly

With a “traditional” French leader (i.e.NOT the ultra thin “Spanish” and “Nymph au fil” leaders), it is very easy to cast a dry fly without using the weight of your main fly line. The taper and chemical treatment/texture of the leader makes it easy to cast like a fly line.

However, unlike a fly line, it is MUCH easier to hold that leader off the water and take drag out of the equation completely. For pocket water (and also ultra spooky fish) this approach can be an incredibly effective way of dry fly fishing for trout.

I recommend rods of AFTM #3 and BELOW for this tactic – and long rods (over 10-ft) are a significant advantage for holding that leader off the water.